P18-6 Sampling Rate Discrimination: 44.1 kHz vs. 88.2 kHz—Amandine Pras, Catherine Guastavino, McGill University - Montreal, Quebec, CanadaIt is currently common practice for sound engineers to record digital music using high-resolution formats, and then down sample the files to 44.1 kHz for commercial release. This study aims at investigating whether listeners can perceive differences between musical files recorded at 44.1 kHz and 88.2 kHz with the same analog chain and type of AD-converter. Sixteen expert listeners were asked to compare 3 versions (44.1 kHz, 88.2 kHz, and the 88.2 kHz version down-sampled to 44.1 kHz) of 5 musical excerpts in a blind ABX task. Overall, participants were able to discriminate between files recorded at 88.2 kHz and their 44.1 kHz down-sampled version. Furthermore, for the orchestral excerpt, they were able to discriminate between files recorded at 88.2 kHz and files recorded at 44.1 kHz. Convention Paper 8101

Thanks all for your interest in our paper,I received an invitation from hydrogenaudio to provide further details on our work. Thus I will do my best to answer a few questions I could extract from the discussion.

- We used Pyramix 6.0 for down-sampling, as this software is currently used by a lot of audio professionals who produce HD recordings.- Regarding the statistics, the "p" we provided for the results refers to the probability that we got the result by chance. Traditionally for this kind of test (here an ABX), researchers consider that if p<.05, the result is not obtained by chance (as the probability is below 5%), thus participants could discriminate. If .05<p<.1, it may be that the result was not obtained by chance but it's not for sure, that's what is called "a tendency". If the test was easy, we would not need statistics, as participants would have almost 100% of good answers. But this test was extremely challenging for the expert listeners, implying a lot of errors even if some of them could perceive some differences between formats in specific cases (musical excerpt, type of format comparison).- There is no proof that upsampling doesn't introduce artifacts. - Regarding our choice of format comparison and technical chain, our purpose was to investigate perceptive differences between 88.2 vs. 44.1 in "real-life" use of the equipment, thus by taking into consideration what happens in music production and release: in a few cases, music is produced and released in high-resolution (thus playback in high-resolution); in more cases, music is produced in high-resolution and then down-sample into 44.1 for commercial release (thus playback in 44.1); in a lot of cases, music is produced and released in 44.1 (thus playback in 44.1). We used the Fireface DAC as it was the only one that allowed us to switch sample rate with a reasonable delay for the test (less than 1sec.). I wish we could use a better one. However, the Fireface is still pretty good compared to most playback systems people use in their house.

I am a sound engineer myself and started working in research as a part time job 3 years ago. I was glad to work on the high-resolution project as I have heard a lot of discussions in studios and during my sound recording studies on the topic. My main question was if it was worth working in High-Res when the project was to be released in 44.1.This AES paper is the first publication for this study and provides a few answers, maybe not enough for most of us. There will be more stuff coming up. And maybe other labs will work on that topic too as they are A LOT of tests to be done.

Bottom line, although the topic is interesting, mainly these days when the Blue Ray Pure Audio is to be defined, never forget that differences between formats, ADC, DAC,... remain extremely subtle compared to differences between miking techniques, room acoustics, and of courses musicians and their instruments!Best,Amandine

We used the Fireface DAC as it was the only one that allowed us to switch sample rate with a reasonable delay for the test (less than 1sec.). I wish we could use a better one. However, the Fireface is still pretty good compared to most playback systems people use in their house.

It's not clear which Fireface DAC that you used as there are several models. I searched around on the web for some technical tests. I found this test of the Fireface 800:

These results don't look particularly impressive to me. They appear to be to be representitive of hi rez digital players at the lower end of the market.

Lets not criticize where no critic is due.

In any other context, you would have (rightfully) smashed TOS8, ABX, and your contradicting experience into anyones face, who had claimed that a DAC with the capabilities of the Fireface would not be sufficient for testing and comparing real world music.

The reasons, which have been brought forward for the choice of the Fireface, especially fast sample rate switching and real world setup similarity, are sensible. They wouldn't be, if "real world" had been an excuse for a sub-standard device, but it isn't by any means.

QUOTE (Arnold B. Krueger @ Jul 19 2010, 04:35)

By stating the question as a negative hypothesis, you've automatically made the proof that you have demanded exceedingly difficult or impossible.

Rather, I'll try to restate the problem in a fair and balanced way: Is it possible to upsample without introducing audible artifacts?

These results don't look particularly impressive to me. They appear to be to be representitive of hi rez digital players at the lower end of the market.

Lets not criticize where no critic is due.

In any other context, you would have (rightfully) smashed TOS8, ABX, and your contradicting experience into anyones face, who had claimed that a DAC with the capabilities of the Fireface would not be sufficient for testing and comparing real world music.

Talking with hi-rez proponents is difficult because for openers, they flaunt TOS8. Their work inherently critizes the idea that conventional measures and criteria are sufficient. They must disresepct the work of the careful experimenters that have gone before them.

When dealing with them I am sometimes motivated for pity for the technological equivalent of dead horses. ;-)

In short, its hard to deal with hi rez proponents on the grounds of science and reason as we understand them.

So, searching about for some common ground, I noticed the claim that the performance of the Fireface 800 (which I have been cricitized for not discerning even though the evidence I presented about it was 100% on target) was characteristic of hi resolultion music players. My point was that it isn't. Check some relevant Stereophile test reports and see what I mean.